Using Frame for Linear Motion?

So I'm planning a coreXY printer with an aluminum extrusion frame. I've been thinking about using the aluminum extrusions for both the frame and the linear motion system. I'm not sure on the straightness of my extrusions yet but if they have a similar tolerance to smooth rods then I don't see much wrong with it. Does anyone see anything wrong with using the extrusions for linear motion as well as the frame?

I'd be doing something similar to the Modrian/ Foldarap 2 [reprap.org] which seemed to work pretty well.

I'm in the same boat as you and have been designing one using standard aluminum extrusions. The issues I've been running into is finding a reliable linear bearing system for it. One could go the v-slot route, but then it defeats the purpose since an assembled v-wheel goes for $4 a piece. The most promising/economical route I've investigated is a carriage that uses printed wheels. I've tried to use a box carriage, with bearings riding on the surface, but than you run into the wear problems along with issues with pre-loading. I think printed wheels with center bearings riding in the T-slots is the route I will pursue.

Personally went for an OpenBeam extrusion setup with the 15x15mm extrusions.

Made a square box frame and from there added connections on the inside where smooth rods were placed into. Using bronze sintered bushings for the linear motion.

However, I have chosen for 8mm smooth rods, and I think they are a bit too flexy in the middle. Will have to see if this is ideal, otherwise I might replace them with something else. Currently wrestling my way through designing a good system to move the Y-carriage so it's still a long way from being finished.

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http://www.marinusdebeer.nl/

I purchased the extrusions I thought I would need a little while back from Automation4Less. I got in touch with them through email and apparently their extrusions have a straightness tolerance of 0.0125 in per foot. Here is the technical information catalog Technical Info

I'm going to test printed sliders with a two part C-shape so I can adjust the tension with a couple bolts.

Edit because I suck at hyperlinks

Edited 1 time(s). Last edit at 08/23/2014 12:52PM by Marty56.

Its not going to work very well. thats why the latest revisions are not hbot. i was building the hbot folda2 on my own as he posted the files and all the different versions. .
the plastic corner brackets make it flimsy and the y axis sliders do not have near enough rigity and to much flex. also over constrained so they just flex .

Bearing wise? I had the same problem. 8mm rods and bearings flexed too much.
My answer was, stop messing around with plastic parts and cheapo stuff. I made all aluminum parts and Im using 15mm rails and carriage proper. I made my frame super rigid, put DOWEL PINS! EVERYWHERE!

I am planning attaching the extrusions to each other in the corners instead of relying on plastic parts to hold them together. I would use Mcmaster part number 47065T155 and then surround each corner with a printe part for the look. Do you think this would have the same kind of problems as just having printed corners?

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Marty56
I am planning attaching the extrusions to each other in the corners instead of relying on plastic parts to hold them together. I would use Mcmaster part number 47065T155 and then surround each corner with a printe part for the look. Do you think this would have the same kind of problems as just having printed corners?

I have the OpenBeam corner connectors, those are square aluminium blocks to connect the frame beams.

Besides that I have added printed corner brackets to take out all the flex. Even with the great aluminium corners the frame was a bit flexy. I can make a picture tomorrow of my progress if you want.

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http://www.marinusdebeer.nl/

My CoreXY that i'm bulding have 30x30 alu profile and square blocks. It doesn´t flex at all, and its 560 wide x 470 deep x580 tall (in mm)

Also use some IGUS linear motion parts.

Some photos on the post: Here

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cakeslob
Its not going to work very well. thats why the latest revisions are not hbot. i was building the hbot folda2 on my own as he posted the files and all the different versions. .
the plastic corner brackets make it flimsy and the y axis sliders do not have near enough rigity and to much flex. also over constrained so they just flex .

Bearing wise? I had the same problem. 8mm rods and bearings flexed too much.
My answer was, stop messing around with plastic parts and cheapo stuff. I made all aluminum parts and Im using 15mm rails and carriage proper. I made my frame super rigid, put DOWEL PINS! EVERYWHERE!

Oo Photos please! Would be interested to see what and how you've doweled. I've had similar( ?) thoughts involving an open face bearing with the rail affixed to a more stable length of something rigid with dowels.